Maturity, its standard and maturity index of different fruits and vegetables

 

MATURITY

It is the stage of fully development of tissue of fruit and vegetables only after which it will ripen normally. During the process of maturation the fruit receives a regular supply of food material from the plant. When mature, the abscission or corky layer which forms at the stem end stops this inflow. Afterwards, the fruit depend on its own reserves.

In addition to this, typical flavour and characteristic colour also develop. It has been determined that the stage of maturity at the time of picking influence the storage life and quality of fruit, when picked immature like mango develop white patches or air pockets during ripening and lacking in normal brix acid ratio or sugar acid ratio, taste and flavour.

On the other hand if the fruits are harvested over mature or full ripe they are easy susceptible to microbial and physiological spoilage and their storage life is considerably reduce. Such fruits persist numerous problems during handling, storage and transportation. Therefore, it is necessary or essential to pick up the fruits or vegetables at correct stage of maturity to facilitate proper ripening, distant transportation and maximum storage life.

There are certain guiding principles that have to be followed while harvesting a fruit or vegetable:

1. Harvesting should be done at a stage during the peak growth conditions of fruits or vegetables.

2. Harvesting should coincide with the fruit’s acceptable flavor or appearance.

3. Harvesting should be made at a fruit size required by the market.

4. Harvesting should ensure least mechanical damage thereby enhancing adequate shelf life of fruit.

Maturity indices are important for deciding when a fruit or vegetable should be harvested. This helps in creating marketing flexibility as well as providing acceptable eating quality to the consumers.

On the basis of maturity, fruits and vegetable can be categorized into:

Types of Maturity

1. Horticultural maturity / Harvest maturity: It may be defined as the stage at which a  plant or plant part possesses all the prerequisites for use by consumers for a particular purpose, i.e. local, distant, export market (shipping maturity) or exhibition or processing (processing maturity), culinary maturity, desert maturity etc. Ex. A pod vegetable is matured when it is tender with maximum size.

2. Physiological maturity: It is the stage at which a plant or plant part continues ontogeny (complete developmental history of an organism from egg/spore/ bud etc. to an adult individual) even if detached from the parent plant or the point of origin. It can also be defined as the stage at which a plant or plant part is capable of further development or ripening when it is harvested i.e. ready for eating or processing. Ex. A French bean pod or okra pod is at its physiological maturity when the seeds are fully developed and the pod is lignified which will dehisce with little pressure.

3. Commercial maturity: It is the state of plant organ required by a market. It commonly bears little relation to Physiological maturity and may occur at any stage during development.

Most of the horticultural food products follow a pattern starting from bud initiation stage to development stage and live until their death. The development stage, which is longer in duration, comprises growth, maturation (physiological maturity), ripening, and senescence.

 

 

Some measures of maturity...

• Peel colour - citrus, papaya, pineapple, grapes, mango, strawberry.

• Pulp colour - Mango, apple

• Size - citrus, apple, pear

• Shape - banana, pineapple, litchi, mango

• Drying of plant parts - banana

• Surface characteristics - melon, mango

• Ease of separation from plants - musk melon, grape , mango (tapka stage) Vegetables are harvested at harvest maturity stage, which will allow it to be at its peak condition when it reaches the consumer, it should be at a maturity that allows the produce to develop an acceptable flavour or appearance, it should be at a size required by the market, and should have an adequate shelf life. Time taken from pollination to horticultural maturity under warm condition, skin colour, shape, size and flavour and abscission and firmness are used to assess the maturity of the produce.

Table 2: Time taken from pollination to horticultural maturity

S.No.	Vegetables	Time to harvest Maturity (days)
1.     1	Ridge gourd	5 -6
2.     2	Squash	7 - 8
3.     3	. Brinjal	25 - 40
4.     4	Okra 4 - 6
5.     5	Pepper (green stage)	45 - 55
6.     6	Pepper (red stage)	60 -70
7.     7	Pumpkin (mature)	65 - 70
8.     8	Tomato (mature green)	35 - 45
9.     9	Tomato (red ripe stage)	45 - 60
10.  10	Peas	30 - 35

 

Factors affecting maturity

1. Temperature: Higher temperature gives early maturity. e.g. Gulabi (Pink) grapes mature in 100 days in Western India but only 82 days are enough in the warmer Northern India. Lemon and guava takes less time to mature in summer than in winter. Sun-scorched portions of fruits are characterized by chlorophyll loss, yellowing, disappearance of starch and other alcohol insoluble material, increase in TSS content, decrease in acidity and softening.

2. Soil: Soil on which the fruit tree is grown affects the time of maturity.

e.g. Grapes are harvested earlier on light sandy soils than on heavy clays.

3. Size of planting material: This factor in propagated fruits affects fruit maturity.

e.g. In pineapple, the number of days taken from flowering to fruit maturity was more by planting large suckers and slips than by smaller ones.

4. Closer spacing: Close spacing of hill bananas hastened maturity.

5. Pruning intensity: It enhanced the maturity of Flordasun and sharbati Peaches.

6. Girdling: Process of constricting the periphery of a stem which blocks the downward translocation of CHO, hormones, etc. Beyond the constriction which rather accumulates above it. In Grape vines it hastens maturity, reduces the green berries in unevenly maturity cultivar and lowers the number of short berries. It is ineffective when done close to harvest. CPA has an additive effect with girdling.

There are different methods of determining maturity indices in fruits and vegetables Most of the indices vary according to the fruit type (Thompson, 1996). The common methods of determining the maturity of a fruit are:

1. Visual method: this method largely depends on the outward appearance of the fruit, like skin color, size (mass and volume), presence of dry mature leaves, fullness of fruit, drying of plant body.

2. Physical method: firmness, specific gravity, ease of separation of abscission, etc.

3. Chemical method: total soluble solids (TSS), titratable acidity (TA), TSS: TA ratio, starch content, and so on.

4. Computation method: days from flower bloom or bud initiation stage until optimum fruit development.

5. Physiological method: respiration, aroma development, and so on.

Methods to determine Maturity/ Maturity index for fruits and vegetables

The principles dictating at which stage of maturity a fruit or vegetable should be harvested are crucial to its subsequent storage and marketable life and quality. Post-harvest physiologists distinguish three stages in the life span of fruits and vegetables: maturation, ripening, and senescence. Maturation is indicative of the fruit being ready for harvest. At this point, the edible part of the fruit or vegetable is fully developed in size, although it may not be ready for immediate consumption. Ripening follows or overlaps maturation, rendering the produce edible, as indicated by taste. Senescence is the last stage, characterized by natural degradation of the fruit or vegetable, as in loss of texture, flavour, etc. (senescence ends at the death of the tissue of the fruit). Some typical maturity indexes are described in following sections.

(1)   Skin colour: The loss of green colour of many fruits is a valuble guide to maturity. There is initially a gradual loss in intensity of colour from deep green to lighter green and with many commodities, a complete loss of green colour with the development of yellow, red or purple pigments. Some fruits exhibit no perceptible colour change during maturation. Assessment of harvest maturity by skin colour depends on the judgment of the harvester, but colour charts are available for cultivars, such as apples, tomatoes, peaches, chilli peppers, etc. Although human eye is used to evaluate colour but results can vary considerably due to human differences in colour perception. Therefore, an instrument is used to provide a specific colour value based on the amount of light reflected off the commodity surface or light transmitted through the commodity. This instrument can measure small differences in colour accurately and can be automated in the packing line. This instrument is popularly known as Colour Difference Meter. This instrument use colorimetric method for colour measurement.

(2)   Shape: The shape of fruit can change during maturation and can be used as a characteristic to determine harvest maturity. For instance, a banana becomes more rounded in cross-sections and less angular as it develops on the plant. Mangoes also change shape during maturation. As the mango matures on the tree the relationship between the shoulders of the fruit and the point at which the stalk is attached may change. The shoulders of immature mangoes slope away from the fruit stalk; however, on more mature mangoes the shoulders become level with the point of attachment, and with even more maturity the shoulders may be raised above this point.

(3) Size: Changes in the size of a fruit / vegetable while growing are frequently used to determine the time of harvest. Size is generally of limited value as a maturity index in fruit, though it is widely used for many vegetables, especially those marketed early in their development. With these produce, size is often specified as a quality standard, with large size generally indicating commercial over maturity and under sized produce indicating an immature state. The assumption however, is not always a reliable guide for all purpose. For example, in bananas, the width of the individual fingers can be used to determine harvest maturity. Usually a finger placed midway along the bunch and its maximum width is measured with calipers.

(4) Optical methods: Light transmission properties can be used to measure the degree of maturity of fruits. These methods are based on the chlorophyll content of the fruit, which is reduced during maturation.

5) Heat Units / Degree days: It is a measure of the time required for the development of the fruit to maturity after flowering by measuring the degree days or heat units in a particular environment. It has been found that a characteristic number of heat unit or degree days is required to mature a crop under usually warm conditions, maturity will be advanced and under cooler conditions, maturity is delayed. The number of degree days to maturity is determined over a period of several years by obtaining the algebraic sum from the differences ,plus or minus ,between the daily mean temperatures and a fixed base temperature(commonly minimum temperature at which growth occurs).The average or characteristic number of degree days is then used to forecast the probable date of maturity for the current year and as maturity approaches, it can be checked by other means.

The heat unit summation in terms of Growing Degree Days,

GDD=׆{ Tmax –T min}/2-Tb

Tmax= Maximum temperature

Tmin=Minimum temperature

Tb= base temperature

(6) Aroma: Most fruits synthesize volatile chemicals as they ripen. Such chemicals give fruit its characteristic odour and can be used to determine whether it is ripe or not. These odours may only be detectable by humans when a fruit is completely ripe, and therefore has limited use in commercial situations.

(7) Leaf changes: Leaf quality often determines when fruits and vegetables should be harvested. In root crops, the condition of the leaves can likewise indicate the condition of the crop below ground. For example, if potatoes are to be stored, then the optimum harvest time is soon after the leaves and stems have died. If harvested earlier, the skins will be less resistant to harvesting and handling damage and more prone to storage diseases. Apple leaves turns green to light green and to yellow at maturity.

 (8) Abscission: As part of the natural development of a fruit an abscission layer is formed in the pedicel. For example, in cantaloupe melons, harvesting before the abscission layer is fully developed results in inferior flavoured fruit, compared to those left on the vine for the full period.

(9) Firmness: A fruit may change in texture during maturation, especially during ripening when it may become rapidly softer. Excessive loss of moisture may also affect the texture of crops. These textural changes are detected by touch, and the harvester may simply be able to gently squeeze the fruit and judge whether the crop can be harvested. Today sophisticated devices have been developed to measure texture in fruits and vegetables, for example, texture analyzers and pressure testers; they are currently available for fruits and vegetables in various forms. Ripend watermelon emit dull metallic sound.  A force is applied to the surface of the fruit, allowing the probe of the penetrometer or texturometer to penetrate the fruit flesh, which then gives a reading on firmness. Two commonly used pressure testers to measure the firmness of fruits and vegetables are the Magness-Taylor and UC Fruit Firmness testers. The Agricultural Code of California states that “Bartlett pears shall be considered mature if they comply with one of the following: (a) the average pressure test of not less than 10 representative pears for each commercial size in any lot does not exceed 23lb (10.4 kg). (b) the soluble solids in a sample of juice from not less than 10 representative pears for each commercial size in any lot is not less than 13%”

Figure 2.1 Pressure tester used to measure firmness of fruits and vegetables.

(10) Juice content: The juice content of many fruits increases as the fruit matures

on the tree. To measure the juice content of a fruit, a representative sample of fruit

is taken and then the juice extracted in a standard and specified manner. The juice

volume is related to the original mass of juice, which is proportional to its maturity.

The minimum values for citrus juices are presented in the Table’

Minimum juice values for mature citrus.

Citrus fruit               Minimum juice content (%)

Naval oranges                   30

Grapefruit                        35

Lemons                             25

Mandarins                        33

(11) Oil content and dry matter percentage: Oil content can be used to determine the maturity of fruits, such as avocados. According to the Agricultural Code in California, avocados at the time of harvest and at any time thereafter, shall not contain in weight less than 8% oil per avocado, excluding skin and seed Thus, the oil content of an avocado is related to moisture content. The oil content is determined by weighing 5 -10 g of avocado pulp and then extracting the oil with a solvent (e.g., benzene or petroleum ether) in a distillation column. This method has been successful for cultivars naturally high in oil content.

(12) Moisture content: During the development of avocado fruit the oil content increases and moisture content rapidly decreases. The moisture levels required to obtain good acceptability of a variety of avocados cultivated in Chile are listed in the table given below.

Moisture content of certain varieties of avocado fruit cultivated in Chile.

Cultivar                Moisture content (%)

Bacon                              77.5

Zutano                             80.5

Fuerte                              77.9

Edranol                            78.1

(13) Sugars: In climacteric fruits, carbohydrates accumulate during maturation in the form of starch. As the fruit ripens, starch is broken down into sugar. In non climacteric fruits, sugar tends to accumulate during maturation. A quick method to measure the amount of sugar present in fruits is with a brix hydrometer or a refractometer. A drop of fruit juice is placed in the sample holder of the refractometer and a reading taken; this is equivalent to the total amount of soluble solids or sugar content. This factor is used in many parts of the world to specify maturity.

14) Starch content: Measurement of starch content is a reliable technique used to determine maturity in pear cultivars. The method involves cutting the fruit in two and dipping the cut pieces into a solution containing 4% potassium iodide and 1% iodine. The cut surfaces stain to a blue-black colour in places where starch is present. Starch converts into sugar as harvest time approaches. Harvest begins when the samples show that 65-70% of the cut surfaces have turned blue-black.

(15) Acidity: In many fruits, the acidity changes during maturation and ripening, and in the case of citrus and other fruits, acidity reduces progressively as the fruit matures on the tree. Taking samples of such fruits, and extracting the juice and titrating it against a standard alkaline solution, gives a measure that can be related to optimum times of harvest. Normally, acidity is not taken as a measurement of fruit maturity by itself but in relation to soluble solids, giving what is termed the brix: acid ratio.

(16) Specific gravity: Specific gravity is the relative gravity, or weight of solids or liquids, compared to pure distilled water at 62°F (16.7°C), which is considered unity. Specific gravity is obtained by comparing the weights of equal bulks of other bodies with the weight of water. In practice, the fruit or vegetable is weighed in air, then in pure water. The weight in air divided by the weight in water gives the specific gravity. This will ensure a reliable measure of fruit maturity. As the fruit matures its specific gravity increases. This parameter is rarely used in practice to determine time of harvest, but could be used in cases where development of a suitable sampling technique is possible. It is used however to grade crops according to different maturities at post-harvest. This is done by placing the fruit in a tank of water, wherein those that float are less mature than those that sink.

MATURITY OF FRUITS AND VEGETABLES

Maturity index	Commodity
Peel Colour	Citrus, Papaya, pineapple, tomato (breaker stage), grapes, mango, straw berry and peas
Pulp Colour	Tomato, mango and apple
Size	Asparagus, cucumber, citrus, apple and pears.
Shape	Banana (fullness of fingers,disappeaence of angularity), mango(fullness of  cheeks), pineapple (flattening of eyes with slight hollowness at the centre) and litchi(flattening of tubercles)
Drying of plant parts	Onion,garlic,banana,potato and ginger
Surface characteristics	Grape, tomato, melon and mango

 

Maturity Index	Commodity
TSS	Grape (14-160 brix for Anab-e-shahi, 18-220Brix for Thompson seedless, 12-140 brix for Bangalore blue), mandarin 12-140 brix, sweet orange-120brix, papaya 11.50 brix, pineapple 12-140 brix.
Acidity	Citrus (Mandarin-0.4%, sweet orange 0.3%), mango & pineapple (0.5-0.6%
Ease of separation from plant	Musk melon, grape and mango
Tapping	Watermelon and jackfruit
Netting	Musk melon
Specific gravity	Mango 1.0-1.02 for Alphonso less than 1.0 for dashehari, potato, pineapple (0.98-1.02) & guava (1.00).
Ease of separation from plant	Musk melon, grape and mango
Tapping	Watermelon and jackfruit
Netting	Musk melon

 

•          Tapping - watermelon

• Aroma - jackfruit

• Specific gravity - Mango, pineapple, guava

• Firmness - Melons, apple, pear

• Sugars - Melon and grapes

• TSS - Grapes, sweet orange, papaya

• Acidity - Citrus, mango, pineapple

• Starch index - apple, pear, banana

• Juice content - Citrus

• Heat units - Mango, grape, apple , pear

• Days from anthesis - Melons, pineapple

• Days from full bloom - mango, citrus, apple, pear

• Days from fruit set - banana, mango

Banana

The fruit is harvested when the ridges on the surface of skin change from angularity to round i.e. after the attainment of 3% full stages. Dwarf banana are ready for harvest within 11- 14 months after planting while tall cultivars takes about 14-16 months to harvest. Peel colour change from dark green to light green the remaining style ends were dry, and brittle and fruits were less angular in shape.

• No. of days from fruit set: 90 days

• Pulp:peel ratio = 1.3 to 1.4

• Disappearance of angles

• Brittleness of floral remnants and their natural shedding.

• Dullness of fruit skin colour and odour

• Drying of plant part.

• 75 - 80% maturity

Guava

TSS acid ratio, specific gravity and colour are determined the maturity in guava. For e.g.

• Allahabad safeda - 35.81
• 
  
• Apple colour guava - 26.39
• 
  
• Chittidar guava - 28.13
• 
  
• Lucknow - 49 -34.25
• 
  
• Specific gravity - Less than I
• 
  
• Colour - Light green to yellow.

• Picked at mature green stage (colour change from dark green to light green colour)

• 120 - 150 days after flowering

• TSS 12- 14%

Ber

In ber maturity is judged by colour (yellow), specific gravity (less than 1) and TSS.

• Matures in 150 - 175 days after flowering.

• Green to golden yellow colour.

• TSS: 15-18%

Pomegranate

Sugar percentage should be 12-16% and acid percentage 1.5—2.5%, variety Ganesh

harvest when seed colour becomes pink. In this stage TSS 12.5% and sugar acid ratio 19.5%.

Bael

It takes one year for fruiting after flowering. It is the fruit which ripen after one year of flowering.

Mango

This can be judged when one or two mangoes ripen on the tree are fall on the ground of their own accord. This process of fallen is known as tapaca specific gravity 1,01—1.02 and TSS 10-14%.

• Change in fruit shape (fullness of cheeks) • Change in skin colour from dark green to light green to yellow. • Change in flesh colour from greenish yellow to yellow to orange. • Fruits generally require 95 to 115 days to mature after flowering. • Days from fruit set - 110 to 125 days for Alphonso and pairi • White powdery appearance on fruit surface. • Tapka stage • Decreased acidity, increased aroma and volatile compounds. • TSS : 12 -15% • Specific gravity: • Alphonso : 1-1.02 • Dashehari : <1

GRAPES

• Harvested based on texture of the pulp, peel, colour.

• Easy separation of berries from the bunches & the characteristic aroma.

• In seeded grapes, seeds become dark brown when they fully ripe, while in seedless varieties, characteristic berry colour develops fully.

 • TSS • Bangalore blue : 12 - 14% • Anab-- e-shahi :14 - 16% • Thompson seedless and selection-7 : 19 - 20%

PINEAPPLE

• Flattening of eyes with slight hollow at centre.

• Change of shell colour from green to yellow from base of the fruits.

• Specific gravity : 0.92-1.02%

• TSS: 12 - 14%

• Acidity : 1%

PAPAYA

• Fruits require 125 to 140 days from flowering to maturity.

• Colour of fruit changes from green to pale green or yellowish at blossom end.

 • Usually harvested at 1/4th yellow for export or at 1/2 to 3/4th yellow for local markets.

• Portion of fruit exposed to sunlight becomes dark yellow in colour.

• The latex of fruits becomes watery.

• T.S.S at harvest should be minimum 6%.

APPLE

• Based on colour(external and internal), flesh firmness, composition (starch, sugar acid).

• Change in seed colour to light brown.

• For storage and processing have pressure above 15lbs.

• Ease of separation from spurs

• A starch reading of 5-6 on 1-8 scale is suitable for consumption.

• DFFB : 135-150days.

• 20-40% of cortex clear of starch

PEAR

• Pears are picked unripe.

• Determined by fruit firmness and soluble solids content.

• Fruit size and skin colour.

• DFFB : 120-150Days

PEACH & NECTARINE

• Skin ground colour: green to yellow

• Freeness of pit

• DFFB : 86 - 127 Days

JACKFRUIT

• Colour change from green to yellow to brown.

• .Optimum maturity for jackfruit ranges between 12 and 16 weeks after flower anthesis.

• sound hollow when it is tapped

• Leaf near peduncle starts yellowing.

• Widening of spines and flattening.

• Colour change of carpels.

• Aroma

SAPOTA

 • Fruit with 80% maturity.

• Takes 7-10 1/2 months for anthesis to maturity.

• Ease with which brown scuff gets off the fruit surface.

• Development of yellowish tinge intermixed with corky brown colour on fruit surface. • No green tissue / milky latex on scratching with nails.

CITRUS

• Colour (yellow, orange, red) on 75% of fruit surface .

• Sugar:acid blend

• Mandarin 12 - 14°B

• Sweet orange -12°B

• Acidity: • Mandarin - 0.4% • Sweet orange - 0.3%

• Juice content - 35-50%

Annona

• harvested when they are mature, firm and plumpy, on maturity, fruit turn light green. • The inter aereolar space widens the fruits turn creamy white, the skin between the segments or tubercles turn into light yellow colour.

• For transporting over distant market, the fruits are to be picked before full ripening.

 • DFFB: 100-115 Days

 

 

AONLA

• Colour of the fruit changes from green to greenish yellow.

• Size and weight of the fruits attains it maximum.

• Change in seed colour from creamy-white to brown is an indicator of fruit maturity

AVOCADO

• Changes in fruit colour, fruit size and sometimes oil content.

• In purple variety, fruits are plucked when they show a purplish blush.

• Green type - when they develop yellow tinge and once glossy shine diminishes.

• The area of the stem nearest the fruit changes from a green to brown or black colour when the fruit is mature and ready for harvest.

• The seedcoat typically turns brown when the fruit is sufficiently mature for harvest.

Table 3 Maturity indices of vegetable crops